Efficiency-enhanced TM-mode gyrotron with down-taper interaction structure

被引:0
作者
Yang, Tien-Fu [1 ]
Anariba, Jean Edward Nelson [1 ]
Yao, Hsin-Yu [2 ]
Chang, Chia-Chuan [1 ]
Chang, Tsun-Hsu [1 ]
机构
[1] Natl Tsing Hua Univ, Dept Phys, Hsinchu 30013, Taiwan
[2] Natl Chung Cheng Univ, Dept Phys, Chiayi 621301, Taiwan
关键词
HIGH-POWER; WAVE; MECHANISMS;
D O I
10.1063/5.0239852
中图分类号
O35 [流体力学]; O53 [等离子体物理学];
学科分类号
070204 ; 080103 ; 080704 ;
摘要
Recent advancements have shown that transverse magnetic (TM)-mode gyrotrons are feasible under specific conditions, yet their capabilities remain insufficiently explored. This article systematically investigates a W-band TM11-mode gyrotron within the down-tapered structure(s) to uncover its limitations and underlying physics. 2D interaction-efficiency maps are scanned as functions of the tube's geometrical parameters or beam parameters under magnetic-field tuning. An oversized tube integrated with short two-stage down tapers enhances the output efficiency of the fundamental axial mode and effectively alleviates the axial-mode competition. The peak electron-beam efficiency of the TM11 mode exceeds 50% with an idealized cold beam. The 3D particle-in-cell simulations are utilized to validate the real-time scheme including multiple transverse modes. Incorporating realistic beam spread, the first-harmonic TM11 mode effectively suppresses the second-harmonic and third-harmonic transverse electric modes with a maximum steady output of 130 kW, corresponding to an interaction efficiency of 37%. Complex dynamics regarding the mode-competing and mode-forming processes are revealed and discussed. This study not only facilitates the exploration of TM-mode gyrotrons but also provides insights into the harmonic gyrotron using the axis-encircling electron beam, where TM modes have more chances to be excited and dominate oscillations.
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页数:9
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